Process and apparatus for producing oxygen and nitrogen in a state of purity from atmospheric air



Apri? 29 1.92%. 1,492,663 E. A. BARBET PROCESS AND APPARATUS FOR PRODUCING OXYGEN AND NITROGEN IN A STATE OF PURII'Y FROM ATMOSPHERIC AIR v Filed Feb. 6, 1918 4 Sheets-Sheet l 9 E A. ARBET PROCESS AND APPARATUS FOR PRODUGING OXYGEN AND NITROGEN IN A STATE OF PURITY FROM ATMOSPHERIC AIR 7 Filed Feb. 6, 1918' 4 Sheets-Sheet 2 I VI 1 ,i i '1 E. A. BAET PROCESS AND APPARATUS FOR PRODUCING OXYGEN AND NITROGEN IN A STATE OF'PURITY FROM ATMOSPHERIC AIR Filed Feb. 6, 1918 4 Sheets-Sheet 5 Fig.2

Aprii 29, 1924. 1,492,063

- A BARBET E. PROCESS AND APPARATUS FOR PRODUCING OXYGEN AND NITROGEN IN A STATE OF PURITY FROM ATMOSPHERIC AIR Filed Feb. 6, 1918 4 Sheets-Shet 4 Fig.2.

ill

turnedto the top plate to effect the Washby the condenser.

condenser 1s to take from the vapours a oer.- 4

Patented Apr. 29,

UNITED STATES P NT- OFFICE;

EMILE aueuszrm Banana, or rams, rmcn.

PROCESS AND A PPAflATUs FOR PRODUCING OXYGEN AND NITROGEN IN A STATE PURITY FROM ATMOSPHERIC AIR; 4

5 Application filed February 8, 1918, Serial No. 215,679.

To all whom it may concern:v

Be it known that I, EMILE AUcU's'rIN BARBET, a citizen of the French Republic, residing at No. 5 Rue de lEchelle, Paris, France, have invented certain new and useful Improvements in Processes and APPB? ratus for Producing Oxygen and Nitrogen in a State of Purity from Atmospheric Air, of which the following is a speci cation.

The present invention relates to the production of nitrogen-and oxygen in a state of absolute purity and in a single continuous operation by the continuous rectification of liquidair. i v

The separation of the "constituents of the liquid air is effected by a process analogous to that first applied in the continuous rectification of alcohols and demonstrated by Mr. E. Barbet in 1890, and in which-the-refining of the volatile product is efi'ected almost entirely on the plates of the rectifying column by causing the vapours rising through the rectification column to bubble through a reflux of pure liquid returned to the top plates The sole action of the tain quantity of. the pure product, the re mainder of the condensed liquid belng reing of the ascending vapours. This reflux gradually and methodically forces all the less volatile constituents to the lower parts of the apparatus, permitting only the most volatile to pass over.

The heavy vapours,,that is to say, vapours which are less volatile than the other va-- pours present are condensed in the liquid onthe plates and evaporate in their stead a higher degree of volatility than those of the}:

corresponding weight of more volatile vapour. If the vapours compr se vapours of a product desired to be obtained they will pass through the boiling liquid and not being water circulating m K several degrees, which-5 5 ump. The com- 1 condensed. in the condenser are allowed to pass away.. I v

In the accompanying drawing- Figure 1 is a diagrammatic view of the I device for carrying out the, process of the present invention. I a

Figure 2 1s a v compression due 'to' the modification of this device.

Q In the operation of the apparatus, shown in Figure 1, air, previously freed from CO and moisture by bubbling through NaOH solutiona-nd then throughstrong H SO of 5055 B., or stronger, is supplied to the tank R, in which a pressure is maintained equal to about four atmospheres, by a suitable compressor (not shown) Air from the receptacle R passesthrough pipe 30, heat exchanger D, pipe 31, exchanger C, pipe- 32 into the liquefaction apparatus E, from which the liquid air passes, by its own pressure, through pipe 26, into exchanger I in which it is partly re-evaporated, thence through pipe 39 into the middle a of the column AA at the inlet. P. Another part of the, air from R passes through regulated pipe 33, exchanger G,.pipe 34, exchangerF, pipe 35, into E Where it mixes with the'air entering'the same through pipe 32.

The rectifying apparatus comprises a column having bubblingv (splashing) plates AA of any suitable type. "Air is supplied at a as above stated. The rectificatlon of V the nitrogen-is eflected in the upper part A of the column; the rectification of the oxygen takes column.

A proximately equal to twice that of the output of the apparatus, passes through the-uper pipe A2 of the rectifier, the volume eing regulated by the speed of the pump J and the extent to which the'valve in the connection at is opened.' The liquefaction ofvolumeof cold gaseous nitrogen, ap-

this gaseous nitrogen which-is to form the reflux liquid in column is eflected as fo1--- lows:l-The nitrogen is compressedto a pressure of twoor three atmos" heres by means of the pump J, and is refrigerated by cold gaseous nitrogen passing to the pump J by way of the exchangerIL'pipe 20 andcoil K.

The nitrogen passing through K cools the water is then used to remove the heat of pressed nitrogencpassing rom J through 21 A loses its'heat o'fvcompressio'n in the cooling device K: which is supplied, with water placein the lower part A of the from the bottom' of H by pipe 23.

I passes through pipe 22 into the exchanger H where it is refrigerated by the nitrogen drawn in by the pump through pipe A2.

Thus we have compressed nitrogen the temperature of which 1s ahnost the same as that leaving the top of column A passing nitrogen passes into the exchanger '15 where 26, this liquid air being produced in'another- The nitrogen it comes in temperature-exchanging relation with liquid nitrogen withdrawn from column A at m through the pipe 24. .The cooled, but not yet liquefied nitrogen passes through pipe '25 into the exchanger I in which it is liquefied by the low temperature due to liquid air supplied through the pipe part (E) of the apparatus.

whichis liquefied in I passes through a float densed and thus pass through the liquid. nitrogen on the plate at m without render separator b, which gets rid of some of the non-liquefied traces of more volatile vapours, notably neon and helium, The liquid nitrogen rises by means of its pressure column A at n.

The nitrogen reflux (i. e., that introduced in the liquid state at n) is not chemically pure since, owing to the rapidity of its con densation it has taken in addition to'nitrogen, also neon and helium. The whole (except the portion of the neon and helium vented at N) is caused to flow back upon the head plate where this liquid is subjected anew to ebullition by the nitrogen vapours bubblin up there. In accordance with the f laws 0 ments are first converted back into vapour and after bubbling up on one or two plates,

ebullition the most volatile elethe reflux liquid is freed from such elements if an outlet for these is provided.

The nitrogen vapours rising from the lower-plates contain very slight quantities of neon and helium, those vapours being more-volatile than nitrogen, cannot be coni use of liquid air at I to complete the 'into the to 27; The ot er half of the liquid nitrogen assin liquefication of the nitrogen of the column t roug pipe continues to drop from plate to plate to column.

through pipe 2'7 and enters the top of back regulated to permit of the discharge of the desired volume to the gasonieter.

The cold of the pure gaseous nitrogen is used to provide a certain weight of very cold air which cooperates in supplying the rectifier. The air is drawn in a compressed state, from reservoir R through pipe 30 and passes into the exchanger D which is supplied with water through S, whereby, the air is cooled, then the air passes through pipe 31 into exchanger C where it is cooled by being brought into heat-conducting relation with the gaseous nitrogen. From there it passes through ipe 32 into the tubular shell E to be lique ed by reason of its own pressure, as will be explained hereinafter.

It is possible to increase the relative power of the nitrogen reflux. It is only necessary to operate the pump J at greater speed. The same quantity of finished, pure nitrogen is continually withdrawn at m, but since a greater weight of reflux will be returned thevolume of nitrogen passing from A will increase by exactly the same amount,

.and the operation will increase by exactly the same amount, and the operation will be self-regulating and accompanied with no inconven1ence, s1nce the llquefactlon of larger amounts of nitrogen in I means revaporization'of more of the liquid air therein, and I 1 hence the introduction of proportionately more revaporized air at P. This process permits of,as nearly. a perfect refining as the industry requires, since'this degree of refining depends directly on the given proportion of the washing liquid, that is of the reflux liquid.

The li uid air dropping from plate to plate in becomes poorer in nitrogen and richer in oxygen. It isnecessary to have a source of heat at the base of A" the function of which is to vaporize the pure oxygen which constitutes the residual liquid of the base of the rectifier, this is effected by the tubular member E.

The air which has been forced at a pressure of about 4 atmospheres into reservoir" R is heated by the-compression, and passes through pipe33 into exchanger G where it is cooled by the coldwater brought through S exactly as is done for. the nitrogen .at K.

From I} the compressed air passes through pipe 34; into the tubular exchanger F. 'hilc it is passing around the tubes in F gaseous oxygen, very cold .(about 93 absolute) drawn from the bottom of Aat Ow, wash-the risingvapours in the rect fication is caused to pass inside these same tubes;

The cooled air in F, stlll underpressure air,instead of liquefying at 83 absolute" will be liquefiable at about 99 absolute"; the

finally passes through pipe 35 into the shell of, E and mixes with;the air delivered throiigh 32, while inn-the tubes of the device E there is liquid oxygen of 93 absolute,

which is the final reflux from the column A. This a paratus is connected at its bottom to the col through pipe 36. Owing to its pressure, the

liquid oxygen of 93 is thus itself able to condense it, by being itself revaporized. It

is hence accordingly thus pure oxygen vapipe 38 and coil G, acts to refrigerate the compressed air coming; from container R,

as prevlously .stated, and after passage through measuring device M goes to' the oxygen gasometer.

As to the liquefied air underpressure-produced in :E, (the prevention of the escape of gaseous air being prevented by the auto-- matic float device 6) which is to be, fed to the feed plate a, advantage is taken of the pressure of the air to lift this liquid air through the pipe 26, into the exchanger I. It .is this liquid airwhich has been previously referred, to as the complementary ,tion necessary to complete the of the nitrogen. 'All of the excess remams' in the liquid-state. Then the liquid and the gripper stages by the refluxes and forced to-' agent for liquefying the nitrogen reflux.

Arriving at I the liquid air boils, a part of it being converted into vapour (richer in nitrogen than air), this being in roporique cation vapour both pass, through pipe 39 to the .point P and to the feed plate a. The vapour portion unites with'the vapours rich in nitrogen passing ofi upwardly from the plates; A?, and the two vapours rise together through the plates A to effect the rectification of the nitrogen.

It is clear. that if an increased amount of nitrogen reflux is forced to the top of A a greater proportion of liquid air will consequently vaporize in I while the boiling produced at the bottom of A by the heating element E remains constant. Hence there will be in A (as is absolutely necessary) a quantity of rectification vapour which will be increased, by exactly the supplementary quantity of reflux liquid nitrogen to be evaporated. Operation is then carried on efliciently and automatically without requiring continuous regulation.

Notwithstanding heat insulation, it is not possible to prevent the entrance of a slight amount of the surrounding heat-into the rectifier through the walls. If not guarded umn through pipe 37 and at its top.

against the entire device would become heated and no liquid would remain on the plates. Hence it is absolutely necessary to provide an excess of cold to maintain the operation at the low temperature desired.

For this purpose a tubular exchanger -U is placed at the-side of the rectifier through which tubular exchanger liquid air, coming from a compressor (not shown) is caused to circulate. The liquid air enters at 3 and the very cold vaporized air passes out,

through u to return to the liquefying compressor.

'A certain regulated quantity of the vapours from the rectifier is drawn off at a stage in which there is already consider able richness in oxygen through the valved pipe 0. These vapours being liquefiable at an absolute temperature higher than that of the liquid air .because of their high content of oxygen, liquefy and pass in liquid state, through pipe 10, to the'same plate from which they were extracted. In order to measure the amount of cooling thus efl'ected, a sensitive dial thermometer vt is placed at the selected stage; if therectifier is not sufficiently refrigerated from the liquid air in exchanger U, the thermometer t will rise; it is then necessary to increase the amount of liquid air passing through U. If the thermometer tends'to'drop the amount passing decreased, by adjustment of the cock in plpe y. f

Like nitrogen, oxygen contains its impurities. These are: argon which boils at 187 C.=86 absolute, thatis at a temperature between those of oxygen and nitrogen, also xenon andkrypton which are .appreciably less'volatile than oxygen. 7

It is evident that argon driven from the with an inner downwardly-benttube, for

the purpose of drawing ofi the liquid but not the gas, at the level ofmaximum concentration of argon. I

The cool: s regulated 1n such a manner as to draw off an amount equal to about 1 its 7 to of 1% of the entire amount of gas entering theapparatus so that no trace of a'rgon will remaineither in the oxygen or in the nitrogen. 7

As to the krypton. and xenon, if the extraction ofthe gaseous oxygen is efl'ected at Orv, (that is, several plates above the base of the column) these two impurities will accumulate at the base of the column and in the tubularelement The quantity thereof is prevented from becoming an in-- convenience by effecting a continuous slight withdrawal of liquid at X which consists of xenon krypton and liquid oxygen.: on the Pipe 37, about one fourth, one half o even 130 shown in Figure 1, for liquefying the nitrogen reflux is merely given by way of example.

1 The apparatus shown in Figure 2 is slight- 1y simplified. The compressor J gives a s 1g htly greater pressure to the nitrogen'than the device of Figure 1.

The increased volume of nitrogen issuing from the top of the column exchanges its cold units with the same nitrogen that is highly compressed by J, for instance to about 5 or 6 atmospheres. The compressed nitrogen which is cooled in H is still in the gaseous state.

Instead of liquefying the nitrogen in H in I in the arrangement shown in Figure 1) it is delivered bypipe into the shell of vessel E wherein it is wholly liquetied. As this weight of nitrogen is greater than the weight of air which was delivered into E in. Figure 1 the result is a greater gasification. of oxygen and conse uently a greater boiling power of the recti ying apparatus, and therefore a better-purification.

The nitrogen wholly liquefied in E, passes through the separator e and rises thence by its pressure through pipe 41 up to n where in the liquid state at m.

of exchanger C,

it is delivered upon the top plate of the rectifier in order to constitute the desired COPI- ous nitrogen'reflux. The liquid nitrogen isexpanded in e and consequently there takes place likewise in e, the small automatic gasification which will allow of drawing oif the light gases, namely, neon and helium. at N.

The pure nitrogen will be still drawn ofi Then, through pipe 42, it passes into the casing of exchanger B where it is gasified by abstraction of the heat from the air in the tubes thereof, whereby it will liquefy an almost equal amount of air. This air comes, under pressure, from reservoir R, through pipei),

the tubes of the exchanger D, pipe-4A, the tubes of the exchanger C and pi e 45, %asses through the tubes of the exe ranger and through pipe 46 to the feed P of the rectifier, through separator T.

. The nitrogen vaporized in the exchanger B continues its travel through pipe 4 7, shell pipe 48, shell of exchanger D, pipe 49, then measuring device M, to the gasometer.

As regards the removal of the gaseous third of that oxygen issues from the meter M. This partof the apparatus operates as follows An amount of air equal to about one and out through the meter M to the pure ox gen gasome-ter.

e result is a mixed feeding, namely, about it of the feed enters at P in the form .of liquid air, whilst the complement enters at Qin the form of air which is very cold but is still gaseous. I

The arrangement will bebonsiderably simplified, especially at the top of the app-aratus, if it is not required to extract the. rare gases. As regards the purity of the oxygen, the elimination. of the argon, krypton and xenon is so simple, since it comprises neither exchanger nor cooler, that it is scarcely worth while to dispense with such elimination.

As hereinbefore stated, it is necessary to employ a fairly large number of tempera ture recuperators or exchangers, and these recuperators must be of high efiiciency in order to transfer the cold of the issuing pure gases into-the fresh air which is to enter the apparatus to'be liquefied and rectified.

Having now described my invention what I claim as new and desire to secure by Letters Patent is 1. Apparatus for obtaining pure nitrogen and oxygen from atmospheric air, comprising a plate column, acting as a rectifier; means for supplying liquid air and gaseous air to said column at the central part thereof, a compressor adapted to compress the nitrogen passing out .of the top of the column, means for cooling and liquetyingv said. nitrogen a pipe adapted for bringing the liquefied nitrogen to the first plate of the column. a device located in connection with said pipe for extraction of the rare gases contained in the nitrogen, a withdrawal device on the rectifier for withdrawing a portion of the pure liquid nitrogen; heat exchange elements for cooling and lique'fying compressed air under treatment by heat exchange with said liquid pure nitrogen, an outlet for the pure gaseous n1- passing through pipe 43, is

a trogen; a draw-ofl' for liquid containing argon, located several plates below the supply level of the rectifier; heat exchange elements communicating with the base of the rectifier; a device on the connection between the rectifier and the last mentioned heat exchange elements, .for withdrawing rare gases (xenon and krypton) contained in the liquid rich in oxygen at the base of the rectifier, means for bringing a gashotter than the said liquid rich in oxygen into heat conducting relation therewith in said heat exchange elements, a draw-off for pure gaseous oxygen; heat exchange elements, in which the oxygen passing out cools the .compressed air, an outlet for the pure gaseous oxygen; means for withdrawing, cooling and returning vapors to the same stage of the rectifier, located between the main sup- 2 ply level and to level of Withdrawal of argon material.

2. Apparatus for obtaining pure nitrogen and oxygenifrom atmospheric air comprising a plate column provided at near its central part with means for supplying liquid and gaseous air; a draw-off for impure nitrogen at the top; heat exchange elements and a compressor in which the nitrogen passing out the top of the column is compressed, cooled and partially liquefied by the cold nitrogen passing from the top of the column; means for further cooling and liquefying said nitrogen by liquid air pro,-

. duced in the apparatus; a pipe for returning the liquefied nitrogen to the first plate of the column; on this pipe a device for the extraction of the rare gases contained in the nitrogen; a draw-off located lower down nitrogen; heat excha the liquid nitrogen coo compressedair; an outlet for the pure aseous nitrogen; an extraction device for t e liquid argon some distance below the main sulpply level of the rectifier; a heat exchange e ement communicatin with the base of the rectifier which contains the liquid rich in oxygen; a device for the. removal of 3611011 and krypton on the pipe connecting the base of the rectifier with said heat exchange element, connections for conducting compressed air cooled by the nitrogen tosaid exchange elements; a pipe for bringing the liquidv air produced to 1 the exchange element'in which the ,nitrogen is liquefied; connections for bringing this air partly in the-liquid *and gaseous state to the supply co umn; an extraction device for pure gaseous oxygen from the temperature exchange element in which the oxy en passing o'fl cools the com- -pressed air w 'ch unites in the exchange element at the bottom of the column with the compressed air cooled by the nitrogen; an outlet for the pure gaseous oxygen; a

6 device between the main point otsupply to on the rectifier for a part of the pure liquid e elements in whichartly in the the rectifier and the point at which the argon is extracted for drawing of'f vapors and cooling the same by liquid air and for returning the condensed vapours to the same stage of the rectification column.

3. Apparatus for obtaining pure nitrogen and; oxygen starting with atmospheric air comprising, a plate column with a feed of liquid and a feed of gaseous air both at the center thereof; temperature exchange elements and a compressor in which the nitrogen passing oif from the top of the column is compressed, cooled andliquefied utilizing the cold units of the nitrogen issuing from the top of the column and of the oxygen of the bottom of the column; a pipe for returning the liquefied nitrogen to the first plate of the column; on this pipe a. device for extracting the rare gases contained in the nitrogen; a draw ofi device on the rectifie'r fordrawing ofi' a portion of the pure liquid nitrogen; heat exchange elements for causing the nitrogen to cool' and liquefy compressed air on its way to said column; an outlet for. the pure gaseous nitrogen; draw off connection for argon located sev eral plates below the point of supply of the column; heat exchange elements communicating with the base of the rectifier; an outlet for xenon and krypton on the communicating pipe; an outlet for pure gaseous oxygen; heat exchan e elements. in which the oxygen passing 0 cools the compressed air on itsway, to the column; a separate inlet for vapors on'the rectifier between its loo" point of supply and the point at which the argon is drawn off; a means for cooling these vapors .by liquid air and a conduit for the return of the condensed vapors to the same stage;

4. An apparatus for obtaining pure oxygen and nitrogen from atmospheric air, comprising. a pressure rcservolr; connections therefrom through heat exchange elements and delivering into the middle of a vertically elongated rectifying column; a cyclic purifier and liquefiei' comprising a gas outlet fromthe top of said column, through a heat exchange system, to a compressor andback to the top of said column,-'a drawofl? from-said-cyclic purifier, for withdrawing neon and the like; a second cyclic purifier and vaporizer comprising a liquid draw-off from ,the bottom of saidcolumn through a heat exchange device andback to the bottom of said column, and a draw-oi? from said purifier for withdrawing krypton and the like; a liquid nitrogen dr'aw-oif from the upper part of the column, but below the top thereof a gaseous oxygen draw-ofl from the lower part of the column, but above the bottom thereof; a liquid argon draw-ofi' above said aseous oxygen draw ofl, a cool ing element 111 combination with said column near its middle; and heat exchangers for 13 transferring heat to material leaving the column from each of the materials about to enter said column, substantially as and for the purpose described.

5. An apparatus as covered in claim 4, in which the cooling element is connected to said column at a level below the air inlet but above the argon outlet.

'6. A process. of obtaining pure oxygen and nitrogen from air which comprises introducing a mixture of liquid air and gaseous air at about the same temperature 1nto the middle of a rectifying column, and allowin the liquid portion to fall therein while tlle gaseous portion rises, withdrawing gaseous nitrogen from the top of the column, compressing and liquefying the same, withdrawing lighter and more volatile impurities from the nitrogen liquefying system, reintroducing the remaining purified nitrogen at the top of the column, drawing ofi' a portion ofthe further purified liquid nitrogen at a levelsomewhat below that at which such liquid nitrogen is returned to the column; drawing off a small amount of liquid from the level of the column at which the liquid contains a maximum amount of argon, drawing off gaseous oxygen at a level below that at which the argon-containing liquid is withdrawn, drawing of? liquid oxygen containing krypton and xenon at the bottom of the column, evaporating the said liquid after withdrawing a sufiicient amount to prevent material rise in the percentage otxenon and krypton in the column, reintroducing the remainder of the cold gaseous oxygen, xenon and krypton into the lower part of the column and cooling the column at a point intermediate its height, sufliciently to correspond with the amount of heat taken up by the column from its environment.

7; The process of claim 6 in which the pressure of the liquefied nitrogen lifts the same to the top of the column.

8. In a process for separating and recovering in a single continuous operation in a state otpurity, substantially the whole of the nitrogen and oxygen contained in the air which consists in subjecting the air partly in liquid state and partly in the gasthe rectifier, and drawing off the argon from the plate where this gas and its maximum concentration, drawing off the oxygen containing xenon and krypton from near the bottom of the column, withdrawing a portion of the oxygen, xenon and krypton to the column and extracting the pure oxygen at a point a few plates above the bottom of the column.

9. In the separation-of air into its constituents in a column apparatus, the step of drawing off from the bottom ofthe column, a continuous stream of liquid rich in oxygen drawing oil from said stream a sufficient fraction of the sameto prevent any substantial accumulation of xenon and krypton in the system, evaporating the residue of said stream by the latent heat of cold compressed air to be liquefied, and returning the re-vaporized oxygen to the column at a substantial distance below the point of draw-elf of pure oxygen.

10. In the separation of air into its constituents in a column apparatus, the step of drawing ofl' from the bottom of the column,

a continuous stream of liquid rich in oxygen drawing off from said stream a sutficient fraction of the'same to prevent any substantial accumulation of xenon and krypton in the system, evaporating the rest of the oxygen so drawn off, in heat conducting relation with in-coming gas to be 111- troduced into the system.

In testimony whereof I have signed my name to this specification.

EMILE AUGUSTIN BARBET. Witnesses:

LUCIEN PAILLARD, Crass. P. Pnnssmr. 

